Thoracentesis

Thoracentesis is usually performed under local anesthetic at the bedside. It is most commonly used for diagnostic purposes, but can be therapeutic. Traditionally, thoracentesis is performed using physical examination and chest radiography to identify landmarks for needle insertion into the effusion. However, thoracentesis can be difficult, even in experienced hands. In those instances where fluid is not easily drained or encountered using this technique, ultrasound can be used to document the presence and location of the effusion as well as to guide its drainage (WeiD.9.§^d.t,..et.,al: 1994). Furthermore, in those cases where an attempt at thoracentesis fails, ultrasound can be useful in identifying the cause of the failed attempt (Weing§.rd..t et..ML 19.9.4).

Unguided thoracentesis may fail because there may, in fact, be an absence of pleural fluid, or the thoracentesis site is either below the diaphragm or above the effusion (Weingardt eL§L 1994). Less frequently, the fluid may be loculated, in which case ultrasound guidance may be quite effective ( WejlQgardt,et,a[ 1994).

A successful thoracentesis depends upon optimal patient and clinician comfort. The most widely used and effective position is with the patient sitting with the head down on pillows over a table. The skin should be cleansed generously with antiseptic solution over the site of the effusion, and the needle should be inserted one intercostal space below the onset of percussion dullness and approximately 3 to 5 cm lateral to the spinal column. The skin, subcutaneous tissue, and parietal pleura should be anesthetized with local anesthetic (e.g. 1 per cent lidocaine (lignocaine) with epinephrine (adrenaline)) and a 'finder' needle then introduced directly over the rib to avoid injury to the neurovascular bundle coursing along the rib's inferior edge. Once pleural fluid is aspirated, the thoracentesis needle can be inserted following the same path taken by the 'finder' needle (Quigley 1995). A post-thoracentesis chest radiograph should be taken to exclude the presence of a pneumothorax secondary to the procedure. In those patients having a significant effusion requiring therapeutic thoracentesis, a volume of 1.5 liters is the maximum amount of fluid which should be removed to reduce the risk of re-expansion pulmonary edema (Quigley 1995).

While thoracentesis can provide relief of symptoms, in the case of malignant pleural effusions symptoms commonly recur as the effusion reaccumulates. In this instance, thoracentesis is primarily for diagnostic purposes. It is best not used repeatedly to drain these recurrent effusions because it is inconvenient, painful, and carries a risk of infection into the pleural space as well as a pneumothorax (QuigleyJSQS). Alternative methods of dealing with recurrent effusions are preferable.

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